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<p>JavaScript&#x7684;&#x5B57;&#x7B26;&#x4E32;&#x5C31;&#x662F;&#x7528;<code>&apos;&apos;</code>&#x6216;<code>&quot;&quot;</code>&#x62EC;&#x8D77;&#x6765;&#x7684;&#x5B57;&#x7B26;&#x8868;&#x793A;&#x3002;</p>
<p>&#x5982;&#x679C;<code>&apos;</code>&#x672C;&#x8EAB;&#x4E5F;&#x662F;&#x4E00;&#x4E2A;&#x5B57;&#x7B26;&#xFF0C;&#x90A3;&#x5C31;&#x53EF;&#x4EE5;&#x7528;<code>&quot;&quot;</code>&#x62EC;&#x8D77;&#x6765;&#xFF0C;&#x6BD4;&#x5982;<code>&quot;I&apos;m OK&quot;</code>&#x5305;&#x542B;&#x7684;&#x5B57;&#x7B26;&#x662F;<code>I</code>&#xFF0C;<code>&apos;</code>&#xFF0C;<code>m</code>&#xFF0C;&#x7A7A;&#x683C;&#xFF0C;<code>O</code>&#xFF0C;<code>K</code>&#x8FD9;6&#x4E2A;&#x5B57;&#x7B26;&#x3002;</p>
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<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> hello = <span class="hljs-string">&quot;I\&apos;m \&quot;OK\&quot;&quot;</span>;
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</code></pre>
<p>ASCII&#x5B57;&#x7B26;&#x53EF;&#x4EE5;&#x4EE5;<code>\x##</code>&#x5F62;&#x5F0F;&#x7684;&#x5341;&#x516D;&#x8FDB;&#x5236;&#x8868;&#x793A;&#xFF0C;&#x4F8B;&#x5982;&#xFF1A;</p>
<pre><code class="lang-java">var a = <span class="hljs-string">&quot;\x61&quot;</span>;
</code></pre>
<pre><code class="lang-shell">a =&gt; a   61&#x662F;97&#x7684;16&#x8FDB;&#x5236;&#x8868;&#x793A;
</code></pre>
<p>&#x8FD8;&#x53EF;&#x4EE5;&#x7528;<code>\u####</code>&#x8868;&#x793A;&#x4E00;&#x4E2A;Unicode&#x5B57;&#x7B26;&#xFF1A;</p>
<pre><code class="lang-javascript"><span class="hljs-comment">// &#x8C8C;&#x4F3C;&#x662F; UTF-16&#x7801;&#x4F4D;</span>
<span class="hljs-keyword">var</span> b = <span class="hljs-string">&quot;\u4F60\u597D&quot;</span>;
</code></pre>
<pre><code class="lang-shell">b =&gt; &#x4F60;&#x597D;
</code></pre>
<p>&#x591A;&#x884C;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x7531;&#x4E8E;&#x591A;&#x884C;&#x5B57;&#x7B26;&#x4E32;&#x7528;<code>\n</code>&#x5199;&#x8D77;&#x6765;&#x6BD4;&#x8F83;&#x8D39;&#x4E8B;&#xFF0C;&#x6240;&#x4EE5;&#x6700;&#x65B0;&#x7684;ES6&#x6807;&#x51C6;&#x65B0;&#x589E;&#x4E86;&#x4E00;&#x79CD;&#x591A;&#x884C;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x8868;&#x793A;&#x65B9;&#x6CD5;&#xFF0C;&#x7528;&#x53CD;&#x5F15;&#x53F7; ` &#x8868;&#x793A;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> c = <span class="hljs-string">`first
second
third`</span>;
</code></pre>
<pre><code class="lang-she">c =&gt;
first
second
third
</code></pre>
<p>&#x6A21;&#x677F;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x8DDF;&#x5176;&#x4ED6;&#x8BED;&#x8A00;&#x4E00;&#x6837;&#xFF0C;&#x76F4;&#x63A5;&#x7528; + &#x53F7;&#x8FDE;&#x63A5;&#x3002;</p>
<pre><code class="lang-java">var d = <span class="hljs-string">&quot;world&quot;</span>;
var e = <span class="hljs-string">&quot;hello &quot;</span>+d;
</code></pre>
<pre><code class="lang-she">e =&gt; hello world
</code></pre>
<p>&#x5982;&#x679C;&#x6709;&#x5F88;&#x591A;&#x53D8;&#x91CF;&#x9700;&#x8981;&#x8FDE;&#x63A5;&#xFF0C;&#x7528;<code>+</code>&#x53F7;&#x5C31;&#x6BD4;&#x8F83;&#x9EBB;&#x70E6;&#x3002;ES6&#x65B0;&#x589E;&#x4E86;&#x4E00;&#x79CD;&#x6A21;&#x677F;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x8868;&#x793A;&#x65B9;&#x6CD5;&#x548C;&#x4E0A;&#x9762;&#x7684;&#x591A;&#x884C;&#x5B57;&#x7B26;&#x4E32;&#x4E00;&#x6837;&#xFF0C;&#x7528;&#x53CD;&#x5F15;&#x53F7;`&#xFF0C;&#x4F46;&#x662F;&#x5B83;&#x4F1A;&#x81EA;&#x52A8;&#x66FF;&#x6362;&#x5B57;&#x7B26;&#x4E32;&#x4E2D;&#x7684;&#x53D8;&#x91CF;&#xFF1A;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> d = <span class="hljs-string">&quot;world&quot;</span>;
<span class="hljs-comment">// &#x6CE8;&#x610F;&#x8FD9;&#x91CC;&#x7528;&#x53CD;&#x5F15;&#x53F7;</span>
<span class="hljs-keyword">var</span> f = <span class="hljs-string">`hello <span class="hljs-subst">${d}</span>`</span>;
</code></pre>
<pre><code class="lang-shell">f =&gt; hello world
</code></pre>
<p>&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x5E38;&#x89C1;&#x65B9;&#x6CD5;&#xFF1A;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">var</span> h = <span class="hljs-string">&quot;hello world&quot;</span>;
<span class="hljs-comment">// &#x83B7;&#x53D6;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x957F;&#x5EA6;</span>
<span class="hljs-keyword">var</span> length = h.length;
<span class="hljs-comment">// &#x5B57;&#x7B26;&#x4E32;&#x53EF;&#x4EE5;&#x770B;&#x4F5C;&#x662F;&#x6570;&#x7EC4;</span>
<span class="hljs-keyword">var</span> index = h[<span class="hljs-number">2</span>];
<span class="hljs-comment">/*
* &#x9700;&#x8981;&#x7279;&#x522B;&#x6CE8;&#x610F;&#x7684;&#x662F;&#xFF0C;&#x5B57;&#x7B26;&#x4E32;&#x662F;&#x4E0D;&#x53EF;&#x53D8;&#x7684;&#xFF0C;
* &#x5982;&#x679C;&#x5BF9;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x67D0;&#x4E2A;&#x7D22;&#x5F15;&#x8D4B;&#x503C;&#xFF0C;
* &#x4E0D;&#x4F1A;&#x6709;&#x4EFB;&#x4F55;&#x9519;&#x8BEF;&#xFF0C;&#x4F46;&#x662F;&#xFF0C;&#x4E5F;&#x6CA1;&#x6709;&#x4EFB;&#x4F55;&#x6548;&#x679C;&#xFF1A;
**/</span>
h[<span class="hljs-number">1</span>] = <span class="hljs-string">&apos;k&apos;</span>;
<span class="hljs-comment">/*
indexOf()&#x4F1A;&#x641C;&#x7D22;&#x6307;&#x5B9A;&#x5B57;&#x7B26;&#x4E32;&#x51FA;&#x73B0;&#x7684;&#x4F4D;&#x7F6E;,
&#x6CA1;&#x6709;&#x627E;&#x5230;&#x6307;&#x5B9A;&#x7684;&#x5B50;&#x4E32;&#xFF0C;&#x8FD4;&#x56DE;-1
 */</span>
<span class="hljs-keyword">var</span> k = h.indexOf(<span class="hljs-string">&quot;world&quot;</span>);
<span class="hljs-comment">/* 
substring()&#x8FD4;&#x56DE;&#x6307;&#x5B9A;&#x7D22;&#x5F15;&#x533A;&#x95F4;&#x7684;&#x5B50;&#x4E32;&#xFF1A;
&#x8DDF;java&#x8BED;&#x6CD5;&#x5DEE;&#x4E0D;&#x591A;
*/</span>
<span class="hljs-keyword">var</span> sub = h.substring(<span class="hljs-number">0</span>,<span class="hljs-number">2</span>);
</code></pre>
<pre><code class="lang-shell">length =&gt; 11
index =&gt; &quot;e&quot;
h[1] =&gt; &quot;e&quot;
k =&gt; 6
sub =&gt; &quot;he&quot;
</code></pre>
<h4 id="&#x6A21;&#x677F;&#x5B57;&#x7B26;&#x4E32;">&#x6A21;&#x677F;&#x5B57;&#x7B26;&#x4E32;</h4>
<p>&#x4F20;&#x7EDF;&#x7684; JavaScript &#x8BED;&#x8A00;&#xFF0C;&#x8F93;&#x51FA;&#x6A21;&#x677F;&#x901A;&#x5E38;&#x662F;&#x8FD9;&#x6837;&#x5199;&#x7684;&#xFF1A;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> string =  <span class="hljs-string">&apos;There are &lt;b&gt;&apos;</span> + basket.count + <span class="hljs-string">&apos;&lt;/b&gt; &apos;</span> +<span class="hljs-string">&apos;items in your basket, &apos;</span> +<span class="hljs-string">&apos;&lt;em&gt;&apos;</span> + basket.onSale +<span class="hljs-string">&apos;&lt;/em&gt; are on sale!&apos;</span>;
</code></pre>
<p>&#x4E0A;&#x9762;&#x8FD9;&#x79CD;&#x5199;&#x6CD5;&#x76F8;&#x5F53;&#x7E41;&#x7410;&#x4E0D;&#x65B9;&#x4FBF;&#xFF0C;ES6 &#x5F15;&#x5165;&#x4E86;&#x6A21;&#x677F;&#x5B57;&#x7B26;&#x4E32;&#x89E3;&#x51B3;&#x8FD9;&#x4E2A;&#x95EE;&#x9898;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> string= <span class="hljs-string">`
  There are &lt;b&gt;<span class="hljs-subst">${basket.count}</span>&lt;/b&gt; items
   in your basket, &lt;em&gt;<span class="hljs-subst">${basket.onSale}</span>&lt;/em&gt;
  are on sale!
`</span>;
</code></pre>
<p>&#x6A21;&#x677F;&#x5B57;&#x7B26;&#x4E32;&#xFF08;template string&#xFF09;&#x662F;&#x589E;&#x5F3A;&#x7248;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x7528;&#x53CD;&#x5F15;&#x53F7;&#xFF08;`&#xFF09;&#x6807;&#x8BC6;&#x3002;&#x5B83;&#x53EF;&#x4EE5;&#x5F53;&#x4F5C;&#x666E;&#x901A;&#x5B57;&#x7B26;&#x4E32;&#x4F7F;&#x7528;&#xFF0C;&#x4E5F;&#x53EF;&#x4EE5;&#x7528;&#x6765;&#x5B9A;&#x4E49;&#x591A;&#x884C;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x6216;&#x8005;&#x5728;&#x5B57;&#x7B26;&#x4E32;&#x4E2D;&#x5D4C;&#x5165;&#x53D8;&#x91CF;&#x3002;</p>
<p>&#x5927;&#x62EC;&#x53F7;&#x5185;&#x90E8;&#x53EF;&#x4EE5;&#x653E;&#x5165;&#x4EFB;&#x610F;&#x7684; JavaScript &#x8868;&#x8FBE;&#x5F0F;&#xFF0C;&#x53EF;&#x4EE5;&#x8FDB;&#x884C;&#x8FD0;&#x7B97;&#xFF0C;&#x4EE5;&#x53CA;&#x5F15;&#x7528;&#x5BF9;&#x8C61;&#x5C5E;&#x6027;&#x3002;</p>
<p>&#x6A21;&#x677F;&#x5B57;&#x7B26;&#x4E32;&#x4E4B;&#x4E2D;&#x8FD8;&#x80FD;&#x8C03;&#x7528;&#x51FD;&#x6570;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">fn</span>(<span class="hljs-params"></span>) </span>{
  <span class="hljs-keyword">return</span> <span class="hljs-string">&quot;Hello World&quot;</span>;
}

<span class="hljs-string">`foo <span class="hljs-subst">${fn()}</span> bar`</span>
<span class="hljs-comment">// foo Hello World bar</span>
</code></pre>
<p>&#x5982;&#x679C;&#x5927;&#x62EC;&#x53F7;&#x4E2D;&#x7684;&#x503C;&#x4E0D;&#x662F;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x5C06;&#x6309;&#x7167;&#x4E00;&#x822C;&#x7684;&#x89C4;&#x5219;&#x8F6C;&#x4E3A;&#x5B57;&#x7B26;&#x4E32;&#x3002;&#x6BD4;&#x5982;&#xFF0C;&#x5927;&#x62EC;&#x53F7;&#x4E2D;&#x662F;&#x4E00;&#x4E2A;&#x5BF9;&#x8C61;&#xFF0C;&#x5C06;&#x9ED8;&#x8BA4;&#x8C03;&#x7528;&#x5BF9;&#x8C61;&#x7684;<code>toString</code>&#x65B9;&#x6CD5;&#x3002;</p>
<p>&#x6A21;&#x677F;&#x5B57;&#x7B26;&#x4E32;&#x751A;&#x81F3;&#x8FD8;&#x80FD;&#x5D4C;&#x5957;&#x3002;</p>
<pre><code class="lang-javascript">const tmpl = addrs =&gt; `
  &lt;table&gt;
  ${addrs.map(addr =&gt; `
    &lt;tr&gt;&lt;td&gt;${addr.first}&lt;/td&gt;&lt;/tr&gt;
    &lt;tr&gt;&lt;td&gt;${addr.last}&lt;/td&gt;&lt;/tr&gt;
  `).join(&apos;&apos;)}
  &lt;/table&gt;
`;
</code></pre>
<h3 id="repeat&#x65B9;&#x6CD5;">repeat()&#x65B9;&#x6CD5;</h3>
<p><code>repeat</code>&#x65B9;&#x6CD5;&#x8FD4;&#x56DE;&#x4E00;&#x4E2A;&#x65B0;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x8868;&#x793A;&#x5C06;&#x539F;&#x5B57;&#x7B26;&#x4E32;&#x91CD;&#x590D;<code>n</code>&#x6B21;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-string">&apos;x&apos;</span>.repeat(<span class="hljs-number">3</span>) <span class="hljs-comment">// &quot;xxx&quot;</span>
<span class="hljs-string">&apos;hello&apos;</span>.repeat(<span class="hljs-number">2</span>) <span class="hljs-comment">// &quot;hellohello&quot;</span>
<span class="hljs-string">&apos;na&apos;</span>.repeat(<span class="hljs-number">0</span>) <span class="hljs-comment">// &quot;&quot;</span>
</code></pre>
<p>&#x53C2;&#x6570;&#x5982;&#x679C;&#x662F;&#x5C0F;&#x6570;&#xFF0C;&#x4F1A;&#x88AB;&#x53D6;&#x6574;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-string">&apos;na&apos;</span>.repeat(<span class="hljs-number">2.9</span>) <span class="hljs-comment">// &quot;nana&quot;</span>
</code></pre>
<p>&#x5982;&#x679C;<code>repeat</code>&#x7684;&#x53C2;&#x6570;&#x662F;&#x8D1F;&#x6570;&#x6216;&#x8005;<code>Infinity</code>&#xFF0C;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-string">&apos;na&apos;</span>.repeat(<span class="hljs-literal">Infinity</span>)
<span class="hljs-comment">// RangeError</span>
<span class="hljs-string">&apos;na&apos;</span>.repeat(<span class="hljs-number">-1</span>)
<span class="hljs-comment">// RangeError</span>
</code></pre>
<p>&#x53C2;&#x6570;<code>NaN</code>&#x7B49;&#x540C;&#x4E8E; 0&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-string">&apos;na&apos;</span>.repeat(<span class="hljs-literal">NaN</span>) <span class="hljs-comment">// &quot;&quot;</span>
</code></pre>
<h4 id="padstartpadend&#x65B9;&#x6CD5;">padStart,padEnd&#x65B9;&#x6CD5;</h4>
<p>ES2017 &#x5F15;&#x5165;&#x4E86;&#x5B57;&#x7B26;&#x4E32;&#x8865;&#x5168;&#x957F;&#x5EA6;&#x7684;&#x529F;&#x80FD;&#x3002;&#x5982;&#x679C;&#x67D0;&#x4E2A;&#x5B57;&#x7B26;&#x4E32;&#x4E0D;&#x591F;&#x6307;&#x5B9A;&#x957F;&#x5EA6;&#xFF0C;&#x4F1A;&#x5728;&#x5934;&#x90E8;&#x6216;&#x5C3E;&#x90E8;&#x8865;&#x5168;&#x3002;<code>padStart()</code>&#x7528;&#x4E8E;&#x5934;&#x90E8;&#x8865;&#x5168;&#xFF0C;<code>padEnd()</code>&#x7528;&#x4E8E;&#x5C3E;&#x90E8;&#x8865;&#x5168;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-string">&apos;x&apos;</span>.padStart(<span class="hljs-number">5</span>, <span class="hljs-string">&apos;ab&apos;</span>) <span class="hljs-comment">// &apos;ababx&apos;</span>
<span class="hljs-string">&apos;x&apos;</span>.padStart(<span class="hljs-number">4</span>, <span class="hljs-string">&apos;ab&apos;</span>) <span class="hljs-comment">// &apos;abax&apos;</span>

<span class="hljs-string">&apos;x&apos;</span>.padEnd(<span class="hljs-number">5</span>, <span class="hljs-string">&apos;ab&apos;</span>) <span class="hljs-comment">// &apos;xabab&apos;</span>
<span class="hljs-string">&apos;x&apos;</span>.padEnd(<span class="hljs-number">4</span>, <span class="hljs-string">&apos;ab&apos;</span>) <span class="hljs-comment">// &apos;xaba&apos;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x4E2D;&#xFF0C;<code>padStart()</code>&#x548C;<code>padEnd()</code>&#x4E00;&#x5171;&#x63A5;&#x53D7;&#x4E24;&#x4E2A;&#x53C2;&#x6570;&#xFF0C;&#x7B2C;&#x4E00;&#x4E2A;&#x53C2;&#x6570;&#x662F;&#x5B57;&#x7B26;&#x4E32;&#x8865;&#x5168;&#x751F;&#x6548;&#x7684;&#x6700;&#x5927;&#x957F;&#x5EA6;&#xFF0C;&#x7B2C;&#x4E8C;&#x4E2A;&#x53C2;&#x6570;&#x662F;&#x7528;&#x6765;&#x8865;&#x5168;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#x3002;</p>
<p>&#x5982;&#x679C;&#x539F;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x957F;&#x5EA6;&#xFF0C;&#x7B49;&#x4E8E;&#x6216;&#x5927;&#x4E8E;&#x6700;&#x5927;&#x957F;&#x5EA6;&#xFF0C;&#x5219;&#x5B57;&#x7B26;&#x4E32;&#x8865;&#x5168;&#x4E0D;&#x751F;&#x6548;&#xFF0C;&#x8FD4;&#x56DE;&#x539F;&#x5B57;&#x7B26;&#x4E32;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-string">&apos;xxx&apos;</span>.padStart(<span class="hljs-number">2</span>, <span class="hljs-string">&apos;ab&apos;</span>) <span class="hljs-comment">// &apos;xxx&apos;</span>
<span class="hljs-string">&apos;xxx&apos;</span>.padEnd(<span class="hljs-number">2</span>, <span class="hljs-string">&apos;ab&apos;</span>) <span class="hljs-comment">// &apos;xxx&apos;</span>
</code></pre>
<p>&#x5982;&#x679C;&#x7528;&#x6765;&#x8865;&#x5168;&#x7684;&#x5B57;&#x7B26;&#x4E32;&#x4E0E;&#x539F;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x4E24;&#x8005;&#x7684;&#x957F;&#x5EA6;&#x4E4B;&#x548C;&#x8D85;&#x8FC7;&#x4E86;&#x6700;&#x5927;&#x957F;&#x5EA6;&#xFF0C;&#x5219;&#x4F1A;&#x622A;&#x53BB;&#x8D85;&#x51FA;&#x4F4D;&#x6570;&#x7684;&#x8865;&#x5168;&#x5B57;&#x7B26;&#x4E32;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-string">&apos;abc&apos;</span>.padStart(<span class="hljs-number">10</span>, <span class="hljs-string">&apos;0123456789&apos;</span>)
<span class="hljs-comment">// &apos;0123456abc&apos;</span>
</code></pre>
<p>&#x5982;&#x679C;&#x7701;&#x7565;&#x7B2C;&#x4E8C;&#x4E2A;&#x53C2;&#x6570;&#xFF0C;&#x9ED8;&#x8BA4;&#x4F7F;&#x7528;&#x7A7A;&#x683C;&#x8865;&#x5168;&#x957F;&#x5EA6;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-string">&apos;x&apos;</span>.padStart(<span class="hljs-number">4</span>) <span class="hljs-comment">// &apos;   x&apos;</span>
<span class="hljs-string">&apos;x&apos;</span>.padEnd(<span class="hljs-number">4</span>) <span class="hljs-comment">// &apos;x   &apos;</span>
</code></pre>
<p><code>padStart()</code>&#x7684;&#x5E38;&#x89C1;&#x7528;&#x9014;&#x662F;&#x4E3A;&#x6570;&#x503C;&#x8865;&#x5168;&#x6307;&#x5B9A;&#x4F4D;&#x6570;&#x3002;&#x4E0B;&#x9762;&#x4EE3;&#x7801;&#x751F;&#x6210; 10 &#x4F4D;&#x7684;&#x6570;&#x503C;&#x5B57;&#x7B26;&#x4E32;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-string">&apos;1&apos;</span>.padStart(<span class="hljs-number">10</span>, <span class="hljs-string">&apos;0&apos;</span>) <span class="hljs-comment">// &quot;0000000001&quot;</span>
<span class="hljs-string">&apos;12&apos;</span>.padStart(<span class="hljs-number">10</span>, <span class="hljs-string">&apos;0&apos;</span>) <span class="hljs-comment">// &quot;0000000012&quot;</span>
<span class="hljs-string">&apos;123456&apos;</span>.padStart(<span class="hljs-number">10</span>, <span class="hljs-string">&apos;0&apos;</span>) <span class="hljs-comment">// &quot;0000123456&quot;</span>
</code></pre>
<h4 id="trimstarttrimend&#x65B9;&#x6CD5;">trimStart,trimEnd&#x65B9;&#x6CD5;</h4>
<p><a href="https://github.com/tc39/proposal-string-left-right-trim" target="_blank">ES2019</a> &#x5BF9;&#x5B57;&#x7B26;&#x4E32;&#x5B9E;&#x4F8B;&#x65B0;&#x589E;&#x4E86;<code>trimStart()</code>&#x548C;<code>trimEnd()</code>&#x8FD9;&#x4E24;&#x4E2A;&#x65B9;&#x6CD5;&#x3002;&#x5B83;&#x4EEC;&#x7684;&#x884C;&#x4E3A;&#x4E0E;<code>trim()</code>&#x4E00;&#x81F4;&#xFF0C;<code>trimStart()</code>&#x6D88;&#x9664;&#x5B57;&#x7B26;&#x4E32;&#x5934;&#x90E8;&#x7684;&#x7A7A;&#x683C;&#xFF0C;<code>trimEnd()</code>&#x6D88;&#x9664;&#x5C3E;&#x90E8;&#x7684;&#x7A7A;&#x683C;&#x3002;&#x5B83;&#x4EEC;&#x8FD4;&#x56DE;&#x7684;&#x90FD;&#x662F;&#x65B0;&#x5B57;&#x7B26;&#x4E32;&#xFF0C;&#x4E0D;&#x4F1A;&#x4FEE;&#x6539;&#x539F;&#x59CB;&#x5B57;&#x7B26;&#x4E32;&#x3002;</p>
<pre><code class="lang-javascript"><span class="hljs-keyword">const</span> s = <span class="hljs-string">&apos;  abc  &apos;</span>;

s.trim() <span class="hljs-comment">// &quot;abc&quot;</span>
s.trimStart() <span class="hljs-comment">// &quot;abc  &quot;</span>
s.trimEnd() <span class="hljs-comment">// &quot;  abc&quot;</span>
</code></pre>
<h2 id="&#x5B57;&#x7B26;&#x4E32;&#x4E0E;&#x6570;&#x7EC4;">&#x5B57;&#x7B26;&#x4E32;&#x4E0E;&#x6570;&#x7EC4;</h2>
<p>&#x5B57;&#x7B26;&#x4E32;&#x53EF;&#x4EE5;&#x88AB;&#x89C6;&#x4E3A;&#x5B57;&#x7B26;&#x6570;&#x7EC4;&#xFF0C;&#x56E0;&#x6B64;&#x53EF;&#x4EE5;&#x4F7F;&#x7528;&#x6570;&#x7EC4;&#x7684;&#x65B9;&#x62EC;&#x53F7;&#x8FD0;&#x7B97;&#x7B26;&#xFF0C;&#x7528;&#x6765;&#x8FD4;&#x56DE;&#x67D0;&#x4E2A;&#x4F4D;&#x7F6E;&#x7684;&#x5B57;&#x7B26;&#xFF08;&#x4F4D;&#x7F6E;&#x7F16;&#x53F7;&#x4ECE;0&#x5F00;&#x59CB;&#xFF09;&#x3002;</p>
<pre><code class="lang-js"><span class="hljs-keyword">var</span> s = <span class="hljs-string">&apos;hello&apos;</span>;
s[<span class="hljs-number">0</span>] <span class="hljs-comment">// &quot;h&quot;</span>
s[<span class="hljs-number">1</span>] <span class="hljs-comment">// &quot;e&quot;</span>
s[<span class="hljs-number">4</span>] <span class="hljs-comment">// &quot;o&quot;</span>

<span class="hljs-comment">// &#x76F4;&#x63A5;&#x5BF9;&#x5B57;&#x7B26;&#x4E32;&#x4F7F;&#x7528;&#x65B9;&#x62EC;&#x53F7;&#x8FD0;&#x7B97;&#x7B26;</span>
<span class="hljs-string">&apos;hello&apos;</span>[<span class="hljs-number">1</span>] <span class="hljs-comment">// &quot;e&quot;</span>
</code></pre>
<p>&#x5982;&#x679C;&#x65B9;&#x62EC;&#x53F7;&#x4E2D;&#x7684;&#x6570;&#x5B57;&#x8D85;&#x8FC7;&#x5B57;&#x7B26;&#x4E32;&#x7684;&#x957F;&#x5EA6;&#xFF0C;&#x6216;&#x8005;&#x65B9;&#x62EC;&#x53F7;&#x4E2D;&#x6839;&#x672C;&#x4E0D;&#x662F;&#x6570;&#x5B57;&#xFF0C;&#x5219;&#x8FD4;&#x56DE;<code>undefined</code>&#x3002;</p>
<pre><code class="lang-js"><span class="hljs-string">&apos;abc&apos;</span>[<span class="hljs-number">3</span>] <span class="hljs-comment">// undefined</span>
<span class="hljs-string">&apos;abc&apos;</span>[<span class="hljs-number">-1</span>] <span class="hljs-comment">// undefined</span>
<span class="hljs-string">&apos;abc&apos;</span>[<span class="hljs-string">&apos;x&apos;</span>] <span class="hljs-comment">// undefined</span>
</code></pre>
<p>&#x4F46;&#x662F;&#xFF0C;&#x5B57;&#x7B26;&#x4E32;&#x4E0E;&#x6570;&#x7EC4;&#x7684;&#x76F8;&#x4F3C;&#x6027;&#x4EC5;&#x6B64;&#x800C;&#x5DF2;&#x3002;&#x5B9E;&#x9645;&#x4E0A;&#xFF0C;&#x65E0;&#x6CD5;&#x6539;&#x53D8;&#x5B57;&#x7B26;&#x4E32;&#x4E4B;&#x4E2D;&#x7684;&#x5355;&#x4E2A;&#x5B57;&#x7B26;&#x3002;</p>
<pre><code class="lang-js"><span class="hljs-keyword">var</span> s = <span class="hljs-string">&apos;hello&apos;</span>;

<span class="hljs-keyword">delete</span> s[<span class="hljs-number">0</span>];
s <span class="hljs-comment">// &quot;hello&quot;</span>

s[<span class="hljs-number">1</span>] = <span class="hljs-string">&apos;a&apos;</span>;
s <span class="hljs-comment">// &quot;hello&quot;</span>

s[<span class="hljs-number">5</span>] = <span class="hljs-string">&apos;!&apos;</span>;
s <span class="hljs-comment">// &quot;hello&quot;</span>
</code></pre>
<p>&#x4E0A;&#x9762;&#x4EE3;&#x7801;&#x8868;&#x793A;&#xFF0C;&#x5B57;&#x7B26;&#x4E32;&#x5185;&#x90E8;&#x7684;&#x5355;&#x4E2A;&#x5B57;&#x7B26;&#x65E0;&#x6CD5;&#x6539;&#x53D8;&#x548C;&#x589E;&#x5220;&#xFF0C;&#x8FD9;&#x4E9B;&#x64CD;&#x4F5C;&#x4F1A;&#x9ED8;&#x9ED8;&#x5730;&#x5931;&#x8D25;&#x3002;</p>
<h2 id="base64&#x8F6C;&#x7801;">Base64&#x8F6C;&#x7801;</h2>
<p>&#x6709;&#x65F6;&#xFF0C;&#x6587;&#x672C;&#x91CC;&#x9762;&#x5305;&#x542B;&#x4E00;&#x4E9B;&#x4E0D;&#x53EF;&#x6253;&#x5370;&#x7684;&#x7B26;&#x53F7;&#xFF0C;&#x6BD4;&#x5982; ASCII &#x7801;0&#x5230;31&#x7684;&#x7B26;&#x53F7;&#x90FD;&#x65E0;&#x6CD5;&#x6253;&#x5370;&#x51FA;&#x6765;&#xFF0C;&#x8FD9;&#x65F6;&#x53EF;&#x4EE5;&#x4F7F;&#x7528; Base64 &#x7F16;&#x7801;&#xFF0C;&#x5C06;&#x5B83;&#x4EEC;&#x8F6C;&#x6210;&#x53EF;&#x4EE5;&#x6253;&#x5370;&#x7684;&#x5B57;&#x7B26;&#x3002;&#x53E6;&#x4E00;&#x4E2A;&#x573A;&#x666F;&#x662F;&#xFF0C;&#x6709;&#x65F6;&#x9700;&#x8981;&#x4EE5;&#x6587;&#x672C;&#x683C;&#x5F0F;&#x4F20;&#x9012;&#x4E8C;&#x8FDB;&#x5236;&#x6570;&#x636E;&#xFF0C;&#x90A3;&#x4E48;&#x4E5F;&#x53EF;&#x4EE5;&#x4F7F;&#x7528; Base64 &#x7F16;&#x7801;&#x3002;</p>
<p>&#x6240;&#x8C13; Base64 &#x5C31;&#x662F;&#x4E00;&#x79CD;&#x7F16;&#x7801;&#x65B9;&#x6CD5;&#xFF0C;&#x53EF;&#x4EE5;&#x5C06;&#x4EFB;&#x610F;&#x503C;&#x8F6C;&#x6210; 0&#xFF5E;9&#x3001;A&#xFF5E;Z&#x3001;a-z&#x3001;<code>+</code>&#x548C;<code>/</code>&#x8FD9;64&#x4E2A;&#x5B57;&#x7B26;&#x7EC4;&#x6210;&#x7684;&#x53EF;&#x6253;&#x5370;&#x5B57;&#x7B26;&#x3002;&#x4F7F;&#x7528;&#x5B83;&#x7684;&#x4E3B;&#x8981;&#x76EE;&#x7684;&#xFF0C;&#x4E0D;&#x662F;&#x4E3A;&#x4E86;&#x52A0;&#x5BC6;&#xFF0C;&#x800C;&#x662F;&#x4E3A;&#x4E86;&#x4E0D;&#x51FA;&#x73B0;&#x7279;&#x6B8A;&#x5B57;&#x7B26;&#xFF0C;&#x7B80;&#x5316;&#x7A0B;&#x5E8F;&#x7684;&#x5904;&#x7406;&#x3002;</p>
<p>JavaScript &#x539F;&#x751F;&#x63D0;&#x4F9B;&#x4E24;&#x4E2A; Base64 &#x76F8;&#x5173;&#x7684;&#x65B9;&#x6CD5;&#x3002;</p>
<ul>
<li><code>btoa()</code>&#xFF1A;&#x4EFB;&#x610F;&#x503C;&#x8F6C;&#x4E3A; Base64 &#x7F16;&#x7801;</li>
<li><code>atob()</code>&#xFF1A;Base64 &#x7F16;&#x7801;&#x8F6C;&#x4E3A;&#x539F;&#x6765;&#x7684;&#x503C;</li>
</ul>
<pre><code class="lang-js"><span class="hljs-keyword">var</span> string = <span class="hljs-string">&apos;Hello World!&apos;</span>;
btoa(string) <span class="hljs-comment">// &quot;SGVsbG8gV29ybGQh&quot;</span>
atob(<span class="hljs-string">&apos;SGVsbG8gV29ybGQh&apos;</span>) <span class="hljs-comment">// &quot;Hello World!&quot;</span>
</code></pre>
<p>&#x6CE8;&#x610F;&#xFF0C;&#x8FD9;&#x4E24;&#x4E2A;&#x65B9;&#x6CD5;&#x4E0D;&#x9002;&#x5408;&#x975E; ASCII &#x7801;&#x7684;&#x5B57;&#x7B26;&#xFF0C;&#x4F1A;&#x62A5;&#x9519;&#x3002;</p>
<pre><code class="lang-js">btoa(<span class="hljs-string">&apos;&#x4F60;&#x597D;&apos;</span>) <span class="hljs-comment">// &#x62A5;&#x9519;</span>
</code></pre>
<p>&#x8981;&#x5C06;&#x975E; ASCII &#x7801;&#x5B57;&#x7B26;&#x8F6C;&#x4E3A; Base64 &#x7F16;&#x7801;&#xFF0C;&#x5FC5;&#x987B;&#x4E2D;&#x95F4;&#x63D2;&#x5165;&#x4E00;&#x4E2A;&#x8F6C;&#x7801;&#x73AF;&#x8282;&#xFF0C;&#x518D;&#x4F7F;&#x7528;&#x8FD9;&#x4E24;&#x4E2A;&#x65B9;&#x6CD5;&#x3002;</p>
<pre><code class="lang-js"><span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">b64Encode</span>(<span class="hljs-params">str</span>) </span>{
  <span class="hljs-keyword">return</span> btoa(<span class="hljs-built_in">encodeURIComponent</span>(str));
}

<span class="hljs-function"><span class="hljs-keyword">function</span> <span class="hljs-title">b64Decode</span>(<span class="hljs-params">str</span>) </span>{
  <span class="hljs-keyword">return</span> <span class="hljs-built_in">decodeURIComponent</span>(atob(str));
}

b64Encode(<span class="hljs-string">&apos;&#x4F60;&#x597D;&apos;</span>) <span class="hljs-comment">// &quot;JUU0JUJEJUEwJUU1JUE1JUJE&quot;</span>
b64Decode(<span class="hljs-string">&apos;JUU0JUJEJUEwJUU1JUE1JUJE&apos;</span>) <span class="hljs-comment">// &quot;&#x4F60;&#x597D;&quot;</span>
</code></pre>

                                
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